Hitherto, cellulose fibers, for example, cotton fibers; regenerated cellulose fibers such as viscose rayon (rayon, polynosic, polyviscose, etc.), cuprammonium rayon (Cupra), refined cellulose fibers (for example, Tencel which is solvent-spun cellulose produced by Courtaulds Fibers (UK)), etc.; semisynthetic cellulose fibers such as cellulose acetate (acetate, diacetate, triacetate) fibers, promix (polyacrylonitrile-milk protein graft fiber), etc.; linen fibers; or the like, easily undergo fibrillation. The fibrillation herein denotes a phenomenon in which microfibers forming one fiber are split in the length direction of the fiber. The fibrillation causes whitening of the fiber, thus deteriorating the quality of the fiber. Methods for effectively preventing the fibrillation have not been a suggested to date.
In particular, the refined cellulose fiber has fiber strength stronger than that of rayon and a soft feeling peculiar to rayon. However, since the refined cellulose fiber has a single fiber structure having a uniform and dense fiber cross section instead of a skin-core structure, it is easily fibrillated. The recent researches and developments of the refined cellulose fibers have focused on anti-pilling technologies. Among the refined cellulose fibers, in the refined cellulose fiber in which the fiber surface is intentionally fibrillated by a crumpling and pounding process and then the fibrillated fibers are melted and removed by a cellulase process, pilling hardly occurs. Such a refined cellulose fiber has a feeling of a so-called peach skin finish fabric, and is evaluated as a fiber material suitable for the purpose of the fashion aspect JP 6-322667.
However, the above-mentioned method has problems, for example, the thinning of fibers and a long duration and complicated operation. Thus, it is not a sufficient method because it may deteriorate the strength, or it may lead to the poor operation efficiency. Furthermore, although the peach skin finish fabric may be suitable for the purpose of fashion, it is not suitable for the general-purpose. Thus, the application of the use and using method are limited.
In such circumstances, many methods for preventing the fibrillation by chemically treating fibers have been suggested. Examples of such methods include a method of treating fibers with a bifunctional aldehyde based treating agent (see Publication of JP No. 8-49167 A), a method of treating fibers with diglycidyl ether based treating agent (see Publication of JP No. 9-137384 A), or the like.
In such methods, however, as in usual resin processing methods, the softness of fibers is deteriorated and the fibers cannot practically be used. Furthermore, unevenness in dyeing easily occurs.
Furthermore, a reactive dye, a direct dye, a vat dye, a sulphur dye, a naphthol dye, or the like, is used for dyeing the cellulose fibers. However, each dye has its own effective dye uptake. In general, the dyeing concentration beyond the concentration when the dyeing site of each fiber is dyed cannot be expected. The reactive dyeing achieved by ion bonding (for example, dyeing of nylon and wool with acid dye, dyeing of acrylic fibers with basic dye) has an excellent dyeing efficiency. However, the dyeing efficiency of a reactive dye that reacts with cellulose fiber by covalent bonding is inferior to that by ion bonding. In addition, the dyeing efficiencies of the direct dye, the vat dye, the sulphur dye and the naphthol dye, which bond to cellulose fibers by hydrogen bonding and Van der Waals force, have poorer dyeing efficiency than that by ion bonding, although it is not so poor as the case of the reactive dye. The deterioration of the dyeing efficiency is significantly shown in the case of the deep dyeing. In particular, since the reactive dye uses the most strong and stable chemical bonding, i.e. covalent bonding, it has an excellent wet color fastness. Furthermore, since the reactive dye permits wide range of dyeing in terms of color tone, the consumption of the reactive dye is the greatest in all other dyes used for cellulose fibers. However, the reactive dye has a problem in dyeing efficiency. It is a big challenge to improve the efficiency in dyeing cellulose fibers by direct dyes.